Formula Sheet: Electricity
This chapter introduces electricity, explaining its significance as a vital energy source in various applications. It covers the principles of electric current, circuits, and their regulation.
Mathematical Derivations, Constant Metrics, and Variable Demystification Indices
All engineering, algebraic, and chemical glyph variables are rendered with complete structural precision for Class 10 Science.
Electricity – Formula & Equation Sheet
Essential formulas and equations from Science, tailored for Class X in Science.
This one-pager compiles key formulas and equations from the Electricity chapter of Science. Ideal for exam prep, quick reference, and solving time-bound numerical problems accurately.
Formula sheet
Key concepts & formulas
Essential formulas, key terms, and important concepts for quick reference and revision.
Formulas
I = Q/t
I represents current (amperes), Q is charge (coulombs), and t is time (seconds). This formula calculates the current as the rate of flow of charge. Tip: 1 A = 1 C/s.
V = W/Q
V is potential difference (volts), W is work done (joules), and Q is charge (coulombs). It defines potential difference as work done per unit charge. Example: Moving 2 C with 24 J work gives V = 12 V.
R = ρl/A
R is resistance (ohms), ρ is resistivity (Ωm), l is length (m), and A is cross-sectional area (m²). This shows resistance depends on material and dimensions. Tip: Longer or thinner wires have higher resistance.
P = VI
P is power (watts), V is potential difference (volts), and I is current (amperes). It calculates the power consumed by a device. Example: A bulb at 220 V and 0.5 A uses 110 W.
H = I²Rt
H is heat (joules), I is current (amperes), R is resistance (ohms), and t is time (seconds). Joule's law of heating. Tip: Heat increases with the square of current.
1/Rp = 1/R₁ + 1/R₂ + ...
Rp is equivalent resistance (ohms) of parallel resistors R₁, R₂, etc. The total resistance decreases in parallel. Example: Two 10 Ω resistors in parallel give 5 Ω.
Rs = R₁ + R₂ + ...
Rs is equivalent resistance (ohms) of series resistors R₁, R₂, etc. The total resistance adds up in series. Example: Two 10 Ω resistors in series give 20 Ω.
V = IR
V is potential difference (volts), I is current (amperes), and R is resistance (ohms). Ohm's law, fundamental for circuit analysis. Tip: Directly proportional relationship.
E = VIt
E is energy (joules), V is potential difference (volts), I is current (amperes), and t is time (seconds). Calculates energy consumed by a device. Example: 220 V, 0.5 A for 1 hour is 396 kJ.
P = I²R
P is power (watts), I is current (amperes), and R is resistance (ohms). Alternative power formula, useful when voltage is not known. Derived from P = VI and V = IR.
Equations
Ohm’s Law: V = IR
Defines the relationship between voltage, current, and resistance in a conductor. Essential for solving circuit problems. Real-world use: Designing electrical circuits.
Series Resistance: Rs = R₁ + R₂ + R₃ + ...
Total resistance in a series circuit is the sum of individual resistances. Tip: Current remains the same across each resistor.
Parallel Resistance: 1/Rp = 1/R₁ + 1/R₂ + 1/R₃ + ...
Reciprocal of total resistance in parallel is the sum of reciprocals of individual resistances. Tip: Voltage remains the same across each resistor.
Power: P = V²/R
Calculates power using voltage and resistance. Derived from P = VI and Ohm's law. Useful when current is not directly known.
Current: I = V/R
Calculates current using voltage and resistance. Direct application of Ohm's law. Example: 12 V across 4 Ω gives 3 A.
Energy: E = P × t
Energy consumed is power multiplied by time. Real-world use: Calculating electricity bills. Example: 100 W for 10 hours is 1 kWh.
Resistivity: ρ = RA/l
Relates resistance to material properties and dimensions. Tip: Resistivity is a material property, independent of shape.
Charge: Q = It
Charge is current multiplied by time. Useful for calculating total charge flow. Example: 2 A for 5 seconds is 10 C.
Work: W = VQ
Work done to move charge across a potential difference. Example: Moving 2 C across 12 V requires 24 J.
Heat: H = VIt
Heat produced in a resistor is voltage times current times time. Alternative to H = I²Rt, emphasizing voltage's role.
